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C. W. KECKLER. TELEPHONE SYSTEM; APPLICATION FILED MAY24. 1911.

1,325,871. Patented Dec. 23,1919.

//7 ve/v far: Char/e5 W Keck/er.

by Affy.

UNITED STATES PATENT OFFICE.

CHARLES V. KECKLER, F NEWARK, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRICCOMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

assen.

Specification of Letters Patent.

Patented Dec. 23, 1919.

Application filed May 24, 1917. Serial No. 170,601.

To all who m, itmay concern:

Be it known that I, CHARLES W. KEOKLER, a citizen of the United States,residing at Newark, in the county of Essex and State of New Jersey, haveinvented certain new tems and more particularly to intercommuni- Billeating telephone systems.

The principal object of the invention is to provide a simple andellicient arrangement of circuits and apparatus to effect uniformcommunication between the different stations of the system, and to thisend, electromagnetic means are provided at each station to control theconnection of the home line of a calling station with the line of thecalled station; certain windings of the electromagnetic means atconnected stations also serving as impedance or retardation coilsthrough which talking current is supplied directly to each of two ormore connected lines.

A further object is to enable another station to be brought intotelephonic connection with two or more stations already connected but toaudibly indicate to the stations already connected that an attempt isbeing made to connect in another station. To accomplish this, the relayof the last party called on being energized and signaling anotherstation, connects the line of the called station in the telephoniccircuit of the parties already connected while the transmitter of thecalled station is bridged across the line of that station duringsignaling and an audible signal arranged in proximity thereto whichenables all the stations previously connected to hear the sound producedby the signal at the called station.

This and other features of the invention may be more readily understoodby reference to the accompanying drawing, wherein the invention is shownas applied to an i11- tercominunicating telephone system. Threestations, each having lines extending to the other stations, are shown,although obviously a greater number of stations can be furnished ifdesired. The apparatus and circuits of stations A and B are identicaland while the apparatus at station C is identical with the otherstations, the circuit differs therefrom by controlling the connection ofthe transmitter and receiver across the line of that station through theoperation of its hook-switch, whereas at stations A and B thetransmitter and receiver are permanently brldged across their respectivelines for a reason to be hereinafter described.

In making a call, the calling party will remove his receiver, thussupplying talking batter to his set through two windings of a marginalrelay (not ope ated at this time), these two windings serving asimpedance or retardation coils for the calling line. The calling buttonof the desired station is then depressed and in its lowermost positionsupplies ringing battery through another winding of the relay whichcooperates with the other two windings previously energized to pull upits armature. Ringing battery is also supplied to the hell or othersignal at the called station and as the calling station is connected tothe line called upon the relay pulling up, the calling party can hearthe operation of the signal at the called station provided thetransmitter at the called stationis bridged across its home line duringsignaling; as is the case with stations A and B shown.

The party at the called station would remove his receiver from the hookon answering and thereby supply talking battery directly to the calledline through two of the windings of the relay at the calledstation.

This relay being marginal does not operate under these conditions butthe energized windings serve as retardation coils in supplying talkingbattery to the called station in the same way as the relay at thecalling station. On completion of conversation, the parties hang up andthe talking windings of the relays are deenergized, whereupon thearmature of the relay at the calling station falls back, therebydisconnecting the set from the previously connected line, although thecalling button has not been released from its intermediate position. Onmaking another call the button first operated is automatically releasedby depression of another calling button in the usual manner.

T 0 illustrate the operation more in detail, assume that station Awishes to call station B. Receiver at A would first be removed, therebysupplying current from a common talking battery 5 over a circuitextending from battery 5, conductors 6 and 7 righthand windingofmarginal relay8 individual to station A, conductor 9, switch contact10 in upper position, conductor 11, transmitter'and. receiver of stationA, conductor 12, switchhook 4 and upper contact, conductor 13, middlewinding of relay 8 (wound in series aiding relation to the right-handwinding thereof) and conductors 14 and 6 to the other side of battery 5.The relay 8 is so margined that it will not pull up except onenergization of all three windings WlllCll increases the effectiveampere turns of the relay windings to effect its operation. After being.pulled up, however, this relay w1ll be maintained in operative positionso long as the middle and right-hand windings remain energized.-

:These last mentioned vwindings perform the function of retardationcoils in supply ing talking battery to the set with which they areconnected. This arrangement is important as it supplies each stationwith talking battery. directly through certain windings of the relayindividual thereto, as soon as the receiver is removed from its hook sothat connected stations are each directly supplied with talking current,thus improving communication between the stations and greatly increasingthe transmitting efliciency.

1 After removing his receiver the party at A will depress a calling keyK individual tostation B. This key in common with the other calling keysK, K and K is designed to be depressed as far as it will go in callingso as to contact with the lowermost spring of the key and to engage thecenter spring thereof with a bus bar 15. The keys remain in thelowermost position only so long as they are manually held there by theperson calling, and return to an intermediate position in which they areheld by the usual locking plate 16 as soon as pressure on the callingbutton is relieved. position only the first and second and third andfourth springs, respectively, of the key are engaged. The operation ofany key in calling releases any other key which may have remained inlocked position, although as hereinafter explained, it is not necessarythat keys which may be in locked position at a called station bereleased to obtain connection with the calling line or to preventinterference by other parties; although generally necessary heretoforein systems of this kind.

The bus bar 15 is connected to one side of a ringing battery 17 by aconductor 18, extending to one wire 19 of the common ringing batterywires 19 and 19 and on full depression of the key K a circuit iscompleted to. operate a signal 20 at station B; this. circuit extendingfrom battery 17 conductors 19 and 18, bar 15, third spring of key Kconductor 21, line wire 2, conductor 22, hook switch 23 and lowercontact, conductor 24, armature and winding of sig- In intermediate nal20, conductor 25 and lead wire 19 to the other side of ringing battery.The signal 20 interrupts its own circuit and continues to operate onlyso long as the key K is held in its fully depressed position.

A circuit is also closed at this time to energize the left-hand windingof the relay 8 to cooperate with the other two windings previouslyenergized to pull up the armature thereof. This circuit extends fromsignaling battery 17, conductors 19 and 18, bus bar 15, third spring ofkey K and fourth and fifth springs thereof, conductors 27 and 28,left-hand winding of relay 8, conductors 29 and 19 to the other side ofbattery. The operation of the relay 8 serves to connect the set atstation A with the line wires 2, 2 of station B and inasmuch as thetelephone set of station B is bridged across these line wires duringsignaling, by using an audible signal 20 and locating it in proximitywith the transmitter of the set. the calling party at A will hear thesound of the signal 20 reproduced by the transmitter at station B andwill know that the line is idle and that the signal is being received,whereas if the line is busy, the signal will not be operated and thecalling party hearing nothing will know the called line is busy.Assuming station B to be idle, the circuit to render the operation ofthe signal 20 audible to station A is in parallel with the talkingcircuit of station A. previously traced and commences at conductor 11,thence by conductor 30 to outer arm and front contact of relay 8 (nowenergized), conductors 31 and 32, second and first springs of key Kconductor 33, line wire 2, conductor 3-1, transmitter and receiver ofthe set at station B to conductors 22 and 2, conductor 21, third andfourth springs of key K conductors 36 and 37, inner armature and frontcontact of relay 8, which armature is connected to conductor 12 andcompletes the parallel circuit.

This feature is of considerable advantawc, as hearing the actual soundgiven 011' y the signal at the called station gives a distinctiveindication not liable to be confused with other signals, which hasproved an objectionable feature where tone signals have been used.

If this feature of the invention is not desired for any reason, it isonly necessary to arrange the transmitter so that it is not in circuitwhile its signal is being operated. This may be done by arranging theswitchhook to close the circuit thereto only when the hook is up and thesignal disconnected, and the telephone set at station C illustrates suchan arrangement. The same result may also be obtained by arranging theaudible signal at station C in such a way that the sound therefrom willnot actuate the transmitter orby using a visual rather than an audiblesignal.

The party at station B on hearing his signal would respond by removinghis receiver from the hook, whereupon as previously explained forstation A, talking battery will be supplied directly to the telephoneset of station B through the middle and right-hand windings of relay 38.This circuit extends from battery 5, conductors 6 and 89, right-handwinding oi relay 38, conductor 40, upper position of contact 41,conductor 34:, transmitter and receiver of station B, conductor 22,switchhook 23 and upper contact (now closed), conductor 42, middlewinding of relay 38, conductors 43 and 6, to the other side of battery.Relay 38 being marginal will not pull up when station B is the calledstation as previously explained but the middle and right-hand windingsnevertheless serve as retardation coils in supplying talking batterythereto, thus providing both of the connected stations directly'withtalking battery through their respective relays 8 and 38. This providesbetter transmission than where but one of the stations is supplieddirectly with talking battery and the other stations connected therewithare supplied indirectly through the first station as has been thegeneral practice in intercommunicating systems heretofore.

It will be observed that the connection of station B is independent ofthe position of any of the calling keys thereat, and the line to anystation whose calling key might be in locked position at station B wouldnot be connected, as the only connecting circuit is through theconductors A l and i5 and the front contacts and armatures of the relay38 which is not pulled up while station B is serving as a calledstation.

For the purpose of illustrating how two connected stations can bringanother station in telephonic connection with the connected lines and atthe sam time give an audible indication to those already connected thatsuch an attempt is being made, assume that station A has called stationC and that the two stations are in telephonic communication. Assume thatthe party at station C desires to enable the party at station B to hearor oin in the conversation either with or without the consent of theparty at station A. Station C being the called line, the relay 4:8thereat would not be pulled up although the middle and right-handwindings would be energized. Therefore, the full depression of the key Kindividual to station B, at station C would energize the left-handwinding of the relay 48, which would thereupon pull up, as previouslyexplained for the relay 8, at station A (C now acting as a callingstation). The relay 48 pulling up and cooperating with the K wouldconnect the telephone set at station 0 with the lines wires 2 and 2 ofstation B "LEV and station A being already connected with station Cwould also be connected with the line wires of station B through theapparatus of station 0. At the same time the circuit energizing theleft-hand winding of the relay 48 is closed. The signaling circuit tostation B is also closed to operate the audible signal 20, this circuitbeing similar to that described when station A signaled station B.

Inasmuch as the transmitter of the set at B is bridged across its lineduring signaling and the signal 20 located in proximity thereto, theoperation oi the signal would be audible to station C and also to anyother stations which are in telephonic communication with station C whenthe latter calls station B. In this way, such other stations would beapprised of the fact that an attempt was being made to bring in a partyat another station and enable them to take appropriate action in theevent they did not wish the inclusion of the additional party for anyreason.

The party at station B in responding would remove his receiver from thehook in the usual manner and supply talking current directly to his setthrough the middle and right hand windings of the relay 38 as previouslyexplained. Stations A and C were already in telephonic communication atthe time station C called station B, and as a similar connection isprovided between stations C and B, stations A and B are brought intotelephonic communication through the apparatus at station C so that allthree parties can converse freely together. Disconnection would beeffected by the hanging up of the receivers in the usual manner andresult in the deenergization of the relays 8 and-4c8 in the mannerpreviously described, to restore the apparatus to normal position.

What is claimed is:

1. In a telephone system, a plurality of line circuits, a telephone setassociated with each line circuit, a relay individual to each of saidtelephone sets and having a winding, switching means individual to eachof said telephone sets operable to effect the operation of one of saidrelays to connect two of said line circuits together, and a commonsource of talking current for said telephone system; said winding ofeach of the relays of connected line circuits being interposed betweensaid source of current and its respective telephone set and serving asi1npedance means for talking current supplied to the telephone setindividual thereto during such connection.

2. In a telephone system, a plurality of line circuits, a telephone setincluding a receiver and hook therefor associated with each linecircuit, a relay individual to each telephone set and having a winding,switching means individual to each of said telephone sets operable toeffect the operation of one of said relays to connect two of said linecircuits together, a common source of talking current for said telephonesystem, m ans individual to each telephone set to supply current throughits respective relay to such set directly on removal of the receiver ofthe set from its hook; said relays being interposed between said sourceof current and its respective telephone set and serving as an impedancemeans for talking current supplied to the telephone set individualthereto.

3. In a telephone system, a plurality of line circuits, a telephone setincluding a receiver and a hook associated with each of said linecircuits, a relay individual to each of said telephone sets to connecttwo of said line circuits together, said relay having a plurality ofwinnings, a source of current for said telephone system, meansindividual toeach set to supply current to its respective set through awinding of the relay indi vidual thereto directly on the removal ofitsreceivcr from its hook, switching means for each of said linecircuits adapted to sup ply current through another or said relaywindings to actuate said relay; the first mentioned of said windingsserving as im pedance means for talking current supplied to itsrespective set.

l. In a telephone system, a plurality of line circuits, a telephone setincluding are ceiver and hook associated with each of said linecircuits, a marginal relay having a plurality of windings associatedwith each of said telephone sets to connect two of said line circuitstogether, a source of current for said system, means individualto eachset to control the supply of current to said set through certain oi saidrelay windings on removal of the receiver from its hook, said certain ofsaid relay windings serving as an impedance means, and switching meansassociated with each of said line circuits adapted to supply current tocertain other of said windings to cooperate with the remaining windingsto operate said relay, energization of said impedance windings servingto maintain said relay in operative position.

5. In a telephone system, a plurality of line circuits, a telephone setincluding a receiver associated with each of said line circuits, a relayhaving a plurality of windings and individual to each of said telephonesets to connect two of said lines together, a receiver switch for eachof said sets to supply talking battery to its set directly on removal ofthe receiver through one or more of said relay windings, said one ormore windings serving as impedance means therefor, means at each of saidsets to supply signaling current through one winding of the relay of thecalling set to operate the signal at a called set, said relay requiringenergization of the winding traversed by signaling current in order tooperate and being maintained in operative position by energization ofsaid one or more windings traversed by talking current.

6. In a telephone system, a plurality of line circuits, a plurality oftelephone sets, a relay having a winding and individual to each set toconnect its associated set with one of the line circuits, means forsupplying current to one of the telephone sets through a winding 01" itsrespective relay without operating such relay, and means to increase theeffective ampere turns of such relay to operate such relay to connectits respective set with one of the line circuits.

7. In a telephone system, a plurality of line circuits, a telephone setincluding a transmitter associated with each line circuit, means totelephonically connect two of said line circuits together, meansassociated with one of said connected line circuits to telephonicallyconnect another line circuit to those already connected, an audiblesignal associated with said other line circuit, means operated incidentto connecting said other line circuit to line circuits previouslyconnected to operate said signal, and connections operativelyassociating the transmitter of the set of said other line circuit withsuch circuit during signaling of such set to render the sound producedby said signal audible to the sets oi said previously connected linecircuits through the medium of such transmitter.

8. In a telephone system, a plurality of line circuits, a telephone setcomprising a receiver and transmitter associated. with each linecircuit, means associated with each of said line circuits to connect itto another line circuit, said means being operable only when the linecircuit is the calling line, an audible signal individual to each ofsaid telephone sets and arranged in proximity thereto, and meansoperated incident to the connection of another line circuit to operatesaid signal, the transmitter of the set signaled being connected acrossits line circuit during signaling, whereby the sound produced by saidsignal is communicated to the set of the line calling and also to anyother sets which are in telephonic connection with a line circuitcalling another line circuit.

In witness whereof, I hereunto subscribe my name this 22nd day of May A.D., 1917.

CHARLES W. KECKLER.

